Extended duration fluidic time delay device

ABSTRACT

A fluidic time delay device of long duration is provided by the use of two coacting fluids contained in two chambers separated by an intermediate displacable membrane or piston. The first chamber contains a first fluid consisting of carbon dioxide gas disposed in a pressurized cartridge. The second chamber contains a second fluid consisting of a highly viscous liquid. The first chamber is closed at one end by a screw-on cap provided with means for puncturing the carbon dioxide cartridge as the cap is screwed into place and the second chamber is connected to a capillary tube through which the highly viscous liquid is expelled as the pressure from the carbon dioxide gas forces the intermediate membrane to be displaced across said second chamber.

United States Patent Drzewiecki et al.

[ Oct. 23, 1973 EXTENDED DURATION FLUIDIC TIME 2,889,078 6/1959 Thomas 222/80 DELAY DEVICE [75] Inventors: Tadeusz M. Drzewiecki, T Exam".1er Robert Reeves Gaithersburg M d John M Gum Assistant ExammerJames M. Slattery Falls Church Va AttorneyHarry M. Saragovitz et al.

[73] Assignee: The United States of America as [57] ABSTRACT represented the Secretary of the A fluidic time delay device of long duration is pro- Army washmgton vided by the use of two coacting fluids contained in [22] Filed; J n, 18, 1972 two chambers separated by an intermediate displacable membrane or piston. The first chamber contains [211 App! 218676 a first fluid consisting of carbon dioxide gas disposed in a pressurized cartridge. The second chamber con- [52] U.S. Cl. 60/36, 102/82 tains a Second fluid consisting of a highly visc liq- [51] Int. Cl. Folk 25/00 The first chamber is closed at one end y a w- [58] Field of Search 222/80, 70, 3, 5, on p provided with means for puncturing the carbon 222/4, 547, 564, 476, 477 3865; 192/31 dioxide cartridge as the cap is screwed into place and 82; 60/26,] 39,48 36; 137/68 the second chamber is connected to a capillary tube through which the highly viscous liquid is expelled as [56] References Cit d the pressure from the carbon dioxide gas forces the UNITED STATES PATENTS intermediate membrane to be displaced across said 1,742,604 1 1930 Lemoine 222/5 ux Second chamber 2,105,487 1/1938 Lozon 222/5 X 10 Claims, 1 Drawing Figure IOA I2 IO IOB I8 20 22 4 J11 1 x 4 X |2A\ f g :TJJ:

X I A V I6 PRESSURE RESPONSIVE ORDNANCE DEVICE EXTENDED DURATION FLUIDIC TIME DELAY DEVICE The invention described herein may be manufactured, used and licensed by or for the United States Government for governmental purposes without the payment to us of any royalty thereon.

BACKGROUND OF INVENTION This invention relates to a fluidic time delay device having a delay time capability in the order of hours. The device of this invention may be used as a time delay fuse for explosives or for the delayed operation of a mechanical, flueric or fluidic circuit.

Heretofore long duration time delay devices have been mechanical or electrical in nature. Problems have arisen by the use of electrical and mechanical devices in that they are easily detected and are not sufficiently reliable. Moreover, some radiation enviomments preclude the use of time delay devices containing electronic circuitry.

SUMMARY OF THE INVENTION The long duration time delay device of the present invention makes use of two coacting fluids. A first fluid in the form of an expanding gas is used to force a second highly viscous fluid through a capillary tube. The period of delay is determined by the time required to expell the highly viscous fluid from the capillary tube. The period of delay may be in the order of many hours.

There are six major parameters which determine the duration of fluid efflux from the capillary tube. These are the initial volume of the expanding gas, the initial volume of the highly viscous liquid, the initial gas pressure, the viscosity of the fluid, the length of the capillary tube, and the inside diameter of the capillary. In a preferred embodiment of this invention the time delay may be varied by changing the length of the capillary tube.

After the highly viscous liquid is expelled through the capillary tube the expanding gas is available to power an electrical, mechanical, flueric or fluidic circuit. For example, a circuit can be activated by a fluidic generator whose electrical output charges a capacitor which detonates a booster charge in an ordnance device.

Due to the quasi-steady nature of the liquid efi'lux from the capillary tube the present invention could also be used as a one-shot hydraulic power supply.

In addition the high pressure gas interfaced by the liquid feeding into a second gas chamber could be used to force the second gas out of said second chamber at very low flow rates. Thus, in addition to a low flow of oil, an equally low flow rate of gas for the same duration could be achieved for use in a system requiring low flow rates.

It is an object of the present invention to provide a time delay device having a time delay capability of several hours.

It is a further object of the present invention to provide a time delay device which is safe to use for detonating explosives.

It is a further object of this invention to provide a time delay device which is compact and not easily detected.

It is another object of the present invention to provide a time delay device which may be activated in radiation environments.

It is still another object of the present invention to provide a fluidic time delay device in which the period of delay may be readily adjusted.

These and other objects, advantages and features of the present ivnention will become apparent from the following description and accompanying drawing which is a sectional view of the time delay mechanism embodying the principles of the present invention.

In a preferred embodiment of this invention there is provided a first cylindrical chamber 10 suitably accomodating therein a cartridge 12 containing CO gas under pressure. The cartridge 12 is of conventional design such as those used in water carbonating devices and CO guns. The cartridge 12 is provided with a frangible end portion 12A at one end thereof.

The chamber 10 is provided with external threads 10A at one end. A screw-on cap 14 having internal threads 14A is provided for closing said one end of chamber 10. An O-ring member 16 is disposed between the end of chamber 10 and cap 14 for effecting a hermetic-seal when cap 14 is screwed in place. A pin 14B is disposed on the interior of cap 14 in axial alignment with frangible portion 12A of cartridge 12, so that when cap 14 is screwed in place pin 14B punctures said frangible portion 12A and the CO gas in cartridge 12 is released into chamber 10.

Chamber 10 includes an opening 10B at its other end which is covered by a displacable membrane 18. The membrane 18 may consist of a piston, bellows or plug.

A second chamber 20 is connected to chamber 10 and has an opening 20A in communication with opening 10B. The membrane 18 is displacable in chamber 20 from left to right, as shown in the drawing, by the CO gas released from cartridge 12. Chamber 20' is filled with a highly viscous liquid such as silicone oil of a density on the order of water. These oils are available in viscosity grades from the viscosity of water to 2 X 10 times the viscosity of water.

In a preferred embodiment chamber 20 is provided with a sharp edge efflux orifice 2013. The sharp edge of orifice 208 causes membrane 18 to rupture when it is completely displaced from left to right across chamber 20. This occurs at the end of the time delay period and facilitates the release of the CO, gas to drive an appropriate load device. Instead of using a stretchable membrane 18 which ruptures on the efflux orifice 208, a piston may be provided which passes an opening (not shown) in the side wall of chamber 20 to release the gas to a load device.

There is further provided a capillary tube 22 con nected to the efflux orifice 2013. A mechanism may be provided in tube 22 to vary its length, thus givinga variable duration capability to the time delayperiod.

The operation of the time delay device of the present invention will now be briefly described.

Cartridge 12 is first inserted into chamber 10. Cap 14 is then screwed into place which causes pin 148 to puncture cartridge 12 at 12A and release pressurized CO gas into chamber 10. The CO, expands in chamber 10 forcing membrane 18 to stretch and move to the right. As membrane 18 moves to the right the highly viscous oil in chamber 20 is forced through capillary tube 22. The rate at which the oil passes through capillary tube 22 determines the time delay period. When substantially all of the oil in chamber 20 has been forced into the capillary tube 22, membrane 18 will be punctured by the sharp edge of efflux orifice 2018. At

this time the CO gas will be released to drive an appropriate load device.

It should be understood that the invention is not limited to the exact details of construction shown and described herein for obvious modifications will occur to persons skilled in the art.

What is claimed:

1. In combination, a pressure responsive load device and a pressure generating fluidic time delay device comprising:

a first chamber containing a first fluid;

a second chamber in communication with said first chamber containing a second fluid;

means for initially maintaining said first fluid separate from said second fluid and varying the volume of said second chamber in response to a pressure differential between said first and second chambers;

and capillary means in communication with said second chamber through which said second fluid may pass as the volume of said second chamber decreases;

whereby the period of delay is determined by the time it takes for said second fluid to pass through said capillary means.

2. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 1, wherein said first fluid is a gas under pressure contained within a cartridge and means are provided for releasing said gas into said first chamber to create a pressure differential between said first and second chambersv 3. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 2, wherein said means for releasing said gas comprises end closure means for said first chamber having means thereon for puncturing said cartridge as said end closure is put in closing position.

4. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 2, wherein said gas is carbon dioxide.

5. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 1, wherein said second fluid is a highly viscous liquid.

6. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 5, wherein said highly viscous liquid is silicone oil.

7. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 1, wherein said means for varying the volume of said second chamber comprises a displacable membrane disposed as an interface between said first and second fluids within a first end of said second chamber, whereby a pressure differential between said first and second chambers will cause said membrane to be displaced to a second end of said second chamber.

8. In combinaton, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 7, wherein there is-further provided means for puncturing said displacable membrane as it reaches said second end of said second chamber whereby said first fluid is released to drive said load device.

9. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 8, wherein said load device is a detonating means for an ordnance device.

10. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 1, wherein said capillary means is an elongated tube, the length of said tube determining the duration of the time delay. 

1. In combination, a pressure responsive load device and a pressure generating fluidic time delay device comprising: a first chamber containing a first fluid; a second chamber in communication with said first chamber containing a second fluid; means for initially maintaining said first fluid separate from said second fluid and varying the volume of said second chamber in response to a pressure differential between said first and second chambers; and capillary means in communication with said second chamber through which said second fluid may pass as the volume of said second chamber decreases; whereby the period of delay is determined by the time it takes for said second fluid to pass through said capillary means.
 2. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 1, wherein said first fluid is a gas under pressure contained within a cartridge and means are provided for releasing said gas into said first chamber to create a pressure differential between said first and second chambers.
 3. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 2, wherein said means for releasing said gas comprises end closure means for said first chamber having means thereon for puncturing said cartridge as said end closure is put in closing position.
 4. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 2, wherein said gas is carbon dioxide.
 5. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 1, wherein said second fluid is a highly viscous liquid.
 6. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 5, wherein said highly viscous liquid is silicone oil.
 7. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 1, wherein said means for varying the volume of said second chamber comprises a displacable membrane disposed as an interface between said first and second fluids within a first end of said second chamber, whereby a pressure differential between said first and second chambers will cause said membrane to be displaced to a second end of said second chamber.
 8. In combinaton, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 7, wherein there is further provided means for puncturing said displacable membrane as it reaches said second end of said second chamber whereby said first fluid is released to drive said load device.
 9. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 8, wherein said load device is a detonating means for an ordnance device.
 10. In combination, a suitable pressure responsive load device and a pressure generating fluidic time delay device according to claim 1, wherein said capillary means is an elongated tube, the length of said tube determining the duration of the time delay. 